Digital counter

ABSTRACT

A digital counter in which a continuously rotating group of permanent magnets exerts a constant hysteresis drag individually on the number wheels tending to advance them and in which an escapement when pulsed releases the units wheel to permit rotation to the next digit position. Completion of a cycle of operation of the units wheel releases the tens wheel escapement to permit its wheel to advance to the next digit position and so on in series succession with the hundreds and any additional wheels. Instant resetting is accomplished by disengaging all escapement mechanisms and permitting the wheels to rotate under the hysteresis drag influence simultaneously to engage stops at their zero positions. The individual wheels may be individually set to any desired digit by tripping the individual escapements. A variation on the general scheme is incorporated in a 24 hour clock.

O United States Patent [111 3,5 4,20 2

[HI Inventors Ralph S. Kline; 3,116,875 1/1964 Wolfenden et a1 235/139 Robert A. Olsen, both of Janesville, Wis. 3,189,273 6/1965 Hellen 235/117 I I Appl. No. 2. 3,338,514 8/1967 Weinreich 235/117 523 i::' Primary ExaminerStephen J. Tomsky dV S In Assign Gibbs Manufacturing & Research Attorney Gradolph, Love, Rogers an an civer Corporation Janesville, Wis.

[54] DIGITAL COUNTER ABSTRACT: A digital counter in which a continuously rotating group of permanent magnets exerts a constant hysteresis drag individually on the number wheels tending to advance them and in which an escapement when pulsed releases the units wheel to permit rotation to the next digit position. Completion of a cycle of operation of the units wheel releases the tens wheel escapement to permit its wheel to advance to the next digit position and so on in series succession with the hundreds and any additional wheels. lnstant resetting is accomplished by disengaging all escapement mechanisms and permitting the wheels to rotate under the hysteresis drag intluence simultaneously to engage stops at their zero positions. The individual wheels may be individually set to any desired digit by tripping the individual escapements. A variation on the general scheme is incorporated in a 24 hour clock.

DIGITAL COUNTER BACKGROUND OF THE INVENTION 1. Field of the Invention Impulse actuated wheel type digital counters and related mechanisms.

2 Description of the Prior Art Most digital counters are of the stepping type in which a heavy electromagnet supplies the force to step the number wheels ahead as the magnet is electrically pulsed. The mechanical expedient customarilyused for this purpose is the Geneva movement. Such devices have the characteristic that resistance to the advancing mechanism is high and increases as successive dials or wheels are stepped off. This creates a design difficulty and in general requires heavy electrical current for reliable operation, particularly for resetting. The system also seriously limits speed of operation which is important for some applications. Friction and hence wear is high and this leads to relatively short life not more than a few-million counts at best, and lack of reliability of operation. Partial solutions to some of these problems have been proposed. In Hartkorn US. Pat. No. 3,] 12,068, for instance, individual stepping mechanisms are proposed for the individual wheels so as to obtain faster action by using lighter advancing mechanisms with less inertia. This is possible because each stepping mechanism needs to turn only one wheel and therefore can be lighter and less robust than is necessary when the drive to one wheel must carry over to successive wheels.

SUMMARY OF THE INVENTION This invention in its basic form provides a constantly rotating shaft which is driven in any convenient fashion, by a miniature electric motor of the clock-type for instance, and which rotates independently of the pulse responsive counting mechanism. The number wheels are strung along this shaft and are free to rotate relative thereto. At the ends of the wheel string and between each pair of wheels the shaft is provided with a permanent magnet disc which is adjacent, but does not touch members of high hysteresis material which are secured to or within the wheels. The magnetic system is so polarized that because of the hysteresis effect, the wheels tend to run synchronously with the shaft. They are, however, restrained by a novel and positively acting latching mechanism which holds the wheels stationary individually. An electromagnet when energized or an equivalent mechanism releases the units wheel which then rotates because of the torque developed by the hysteresis effect part way to the next number position and then finishes this single digital increment'of movement when the electromagnet is subsequently deenergized. When the units wheel returns to its zero position a cam trips similar latching mechanism for an increment of movement of the tens wheel, and so on in succession for the hundreds, thousands and higher order wheels if such are provided.

The latching mechanism is so arranged that all latches can be simultaneously disengaged to permit all wheels to rotate freely, and a stop system catches all of the wheels at their zero positions for resetting. The individual wheel latches, beginning with the units wheel and working upwardly, can be individually pulsed as necessary to set into the counter any desired starting number.

Features of the invention are that the electric current required is very low and operation is quite smooth and noise free, about like a clock tick with each number change, even though the wheels can change position substantially instantaneously with almost a snap action. Furthermore, the counting action can be extremely fast for a mechanical counter, and the system is not sensitive either to the counting pulse length, so long as it is long enough to actuate the units latch, norto the number of counting wheels in the string. Friction and hence wear is also extremely low as will appear and service life can readily be many millions of counts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic longitudinal sectional view through a counter which embodies the invention;

FIG. 2 is a diagrammatic end elevation which may be considered as taken along the line 2-2 of FIG. I, so as to eliminate a view obstruction end plate. FIG. 2 also shows certain resetting mechanism which has been eliminated from FIG. 1;

FIGS. 3 to 9 are diagrammatic illustrations used in explaining the successive stages in a counting cycle.

FIG. 10 is a broken longitudinal sectional view showing the invention as embodied in the important portion of a 24 hour clock mechanism. A portion of the structure which will be apparent and essentially repetitive has been omitted in the interest of simplifying the disclosure;

FIG. 11 is a view through the clock window showing a reading on the dials illustrated at approximately 23 hours and 59 minutes, the position of the mechanism in FIG. 10; and

FIG. 12 is a transverse sectional view which may be considered as taken along the line 12-12 of FIG. 10 in the direction indicated by the arrows.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the interest of ready understanding of this invention as embodied in a typical structure, certain of the figures as indicated are largely diagrammatic. In FIG. 1 a rotatable shaft is shown at 10 and this shaft carries magnetic discs l2, 14, 16 and 18 which rotate therewith. The discs in the interest of cost and convenience preferably are fonned of one of the common ceramic permanent magnetic materials and are magnetized so that on each flat face there are six poles, three north alternated with three south equally spaced around a circle located inwardly slightly from the periphery. The poles on opposite faces of the discs are preferably in alignment but this is not essential. The principal advantage is that it aids in assembly. Maximum torque is delivered to the number wheels when the poles on the two sides of each wheel are in alignment, that is, north across from north. About the simplest way to achieve this is to make all of the magnetic discs alike with a keyway or other indexing system used to achieve automatic positioning when the magnets are assembled on the shaft. By having the poles in alignment on the two faces of each disc, no front relative to back difference occurs and hence no orientation as between thetwo faces of the discs is necessary at the time they are pressed or otherwise assembled upon the shaft.

The number wheels, the units wheel is indicated at 20, the tens at 22, and the hundreds at 24, are joumaled upon the shaft 10 in the spaces between the magnet discs 12, I4, 16 and 18. They are free to rotate upon the shaft 10 and do not touch the magnetic discs. The clearance between the wheels and the discs should be a practical minimum. For a particular application, as the clearance appreciably increases it is necessary for the size of the magnets to be increased or a different magnetic material used or some such expedient adopted since, of course, the magnetic inverse square law applies to the situation.

The number wheels may be manufactured in any desired fashion such that they have a bearing surface for the shaft 10 and a cylindrical periphery 11 with equally circumferentially spaced indicia thereon, usually numerals from 0 to 9. The wheels are made of or include an annular disc 25 of material in which the hysteresis losses are high. Any of the well-known materials available for this purpose may be used. The better ones usually are supplied under a proprietory name, depending upon the source. One which has been used successfully is VICALLOY" which is understood to be a heat treated vanadium, iron, cobalt alloy and is produced by Arnold Engineering Company. The effect produced by this assembly is that when the shaft 10 turns at say 1 to 10 revolutions per second, the wheels will rotate synchronously therewith unless restrained. If restrained and then released they will almost instantly accelerate to synchronous speed until again restrained.

Since the torque necessary to rotate the wheels is slight, it will be appreciated that even when all wheels are restrained and the torque reaction is at a maximum, it still is quite low even with a considerable number of wheels. For the purpose of rotating the shaft 10, therefore, a small clock motor geared to have an output drive at l to IO r.p.s. will ordinarily supply adequate torque.

For most purposes a relatively slow speed, such as l r.p.s., is to be preferred since the mechanism makes less noise and there is less wear and shock on the elements than at higher shaft speeds. Also, the power and hence the current requirements are lower and the motor cost is less. Higher speeds are ordinarily suggested only in those applications where the recording of a rapid sequence of counts may be necessary. Much slower speeds can also be used if it is not required that the numbers change quickly when a counting pulse is received, although this is usually considered to be an advantage. At I r.p.s. the interval between number changes and the acceptable interval between counting pulses is only slightly more than a tenth ofa second and this is quick enough for almost all applications.

All of the number wheels 20, 22 and 24 ordinarily will be identical and, therefore, only one needs description. The wheel has an annular groove 26 on the right side as seen in FIG. 1 and a complementary groove 28 on the left. These grooves may be considered as identical excepting'that they face in opposite directions, their interior configurations are offset circumferentially, and there are other minor differences as will appear. The grooves are spaced inwardly of the periphery slightly, enough to provide a full width cylindrical surface 11 for the numerals plus a bit more to accommodate an edge cam to be mentioned presently. The outer larger diameter portion 30 of the groove 26 is continuous. lnwardly of the portion 30, the groove is provided with ten equally spaced toothlike stops or abutments 34 best seen in FIG. 2. These extend outwardly to the flat face of the wheel and have only a narrow dimension circumferentially. The groove '28 is similarly formed with teeth 32, excepting that one tooth is longer than the others and extends across the outer or continuous portion of the groove 28 so as to form a groove interruption at one position. This outer tooth extension serves as a resetting stop as will appear and is indicated by the numeral 36. The teeth 34 are staggered so as to be about half way circumferentially between the similar teeth 32 at the opposite side of the wheel. The left face of the wheel is also provided with an edge cam 38 at the periphery which extends laterally a short distance and which has a tapered face or ramp 40 on its advancing side. The relative circumferential positions of the various elements, such as the cam 38 and the resetting tooth 36 relative to the numbers on the wheel face, depends upon the circumferential location of the escapement mechanism relative to the viewing position or window as will be appreciated.

The escapement mechanism includes an escapement lever for each wheel. All of these can be alike, and are indicated generally at 42. Each lever is formed of relatively heavy sheet metal and is pivoted at about its center upon a pin or screw 44 secured to a vertical escapement mounting plate 58 so that it can rock about an axis above and normal to the shaft axis. The lower portion of the lever is formed to provide a fork which straddles its wheel with inwardly extending pallets 46 and 48 at the fork ends which can intersect the path of movement of the teeth 34 and 32 respectively. The spacing between the ends of the pallets 46 and 48 is such that as the lever is rocked, one of the pallets, 46 for instance, will move into position to intercept the next tooth 34 in its path before the other pallet 48 has released its tooth 32.

An upper extension 50 of each lever, above the pivot 44, has a hole 52 and each of the levers excepting the one for the units wheel has a coil spring 54 hooked therethrough. The opposite ends of these springs are anchored through holes 56 in the escapement plate 58 such that the springs rock the top ends of the levers to the left as seen in FIG; I so as to engage pallets 48 with teeth 32. The units wheel escapement lever 42 is pivoted at its top to the armature or plunger 60 of a solenoid 62 which, when energized, pulls the plunger and the top of the escapement lever to the right. A compression coil spring 64 around the plunger 60 urges the units escapement lever top end to the left when the coil 62 is not energized. Its at rest position is, therefore, the same as that of the other escapements.

Each of the levers 42, other than the units lever, unless it is desired to make all of the levers alike, has a cam following extension 66 on its right side on a position to be engaged by the previously mentioned cam 38 as this cam for the next lower denominational wheel passes the plane of the escapement lever. The cam follower 66 is below the pivot 44 and so once each revolution of the units or tens wheel the respective cam 38 will rock the next higher, tens or hundreds, wheel in the same manner that energizing the solenoid 62 rocks the lever for the units wheel. Pins or screws 68 extending from the backplate 58 on each side of the upward extension 50 of the levers 42 act as limit stops to determine the maximum range of rocking movement of the levers 42.

Basic operation of the escapement system can be most easily appreciated by observing the successive stages shown in the diagrammatic representations, FIGS. 3 to 9. Here the wheel 20 is shown developed and without its peripheral rim 11 so that the center rib and the teeth 32 and 34 show in elevation. It will be assumed that the hysteresis drag tending to rotate the wheel moves the wheel to the right as indicated by the arrow. So as to show change of position, the same portion of the wheel is shown in all figures. As the wheel advances, the portion shown advances toward the right.

In FIG. 3 the system is at rest with a tooth 32 engaging the escapement lever pallet 48. The wheel is held in this position against the torque supplied by hysteresis drag. At this position, pallet 46 is somewhat outside the intercept line of the teeth 34 on the opposite side of the wheel.

In FIG. 4 the solenoid has just been energized and the escapement lever has started to rock. At the instant shown, pallet 48 has not yet released tooth 32, but pallet 46 has already moved inwardly enough to intercept the next tooth 34.

In FIG. 5, pallet 48 has cleared tooth 32 and the wheel has started to move to the right. This wheel motion continues until as shown in FIG. 6, the pallet 46 catches the next tooth 34. So long as the solenoid continues to be energized the elements remain in this condition.

When the solenoid is deenergized, FIG. 7, the escapement starts to return. At the position shown, pallet 46 still engages and holds tooth 34, but pallet 48 has already moved ,inwardly enough to intercept the next tooth 32. In FIG. 8, pallet 46 has released tooth 34 and the wheel is turning. In FIG. 9 tooth 32 has been intercepted by pallet 48 and the at rest starting condition of FIG. 3 restored, excepting that the wheel has moved ahead one increment.

The interval at which cam 38 trips follower 66 during the transition from 9 to 0 can come at any point between FIGS. 5 and 9. Usually, so as to insure the lower order wheel completing its motion first, it will be located at about the stage of FIG. 8.

It should be noted that it is not possible for the system to skip an increment of movement, since one of the pallets 46- 48 is always in an intercepting position and that when the transition is being made from one pallet to another, there is an interval during which both pallets are in the intercepting positron.

The above description is based upon the assumption that the electrical counting pulse is relatively long. It may, however, be quite short. If it is only long enough to work the escapement mechanism to the release position, somewhere between FIGS. 4 and 5 for instance, the ,wheel will start to turn. If theescapement now returns immediately to its starting position, pallet 48 will always be in position to catch the next tooth 32 even in the event that pallet 46 moves outwardly beyond the intercept position before tooth 34 reaches it. The

system, therefore, works equally well on short and long pulses, so long as the pulse is long enough to work the solenoid mechanism to the release position.

When the units wheel 20 almost completes a revolution and is jumping from 9 to 0, the cam 38 engages the cam follower 66 of the tens escapement lever 42 and moves it momentarily to the left as seen in FIG. 1 and then returns it when the cam passes. This releases the tens v. heel 22 for one increment of rotation in the manner outlined above in connection with the description of the units wheel. The same occurs with the hundreds wheel when the tens wheel moves from 9 to 0 and so on with successive wheels if provided.

The escapement mounting plate 58 as previously mentioned carries the pivot pins 44 for the escapement levers and the solenoid mechanism for working the units escapement. As is seen in FIG. 2 this mounting plate has end brackets 70 which extend forwardly and'are pivoted about pins 72 parallel to the shaft 10 suchthat when the plate 58 is rocked about these pins in a counterclockwise direction as seen in FIG. 2 the pallets 48 and 46 are lifted away from the line of teeth 32-34 into the continuous groove 30 and interrupted groove'28. This permits all of the wheels to be free and to rotate until the long tooth extension 36 on each wheel strikes against its pallet 48. This is the zero position for all wheels and so rocking the plate 58 about the pins 72 and then returning it to its original position resets all wheels to zero.

To accomplish this, a lever 74, FIG. 2, extends from the plate 58 and has its free end connected by a pin and fork mechanism 76 to a reset plunger 78. A spring 80 holds the plunger and the escapement system connected thereto to the counting position shown in FIG. 2. Pushing the plunger inwardly rocks the escapement, releases the teeth, and resets all wheels to zero. A pair of pins 82, one on either side of the lever 74, limit movement of the lever 74 and hence the rocking movement of the escapement system between the counting and reset positions.

The circumferential location of the indicia on the wheel peripheries and the position of the viewing window or equivalent relative to the cam 38, the escapement levers, the long reset tooth 36 and the other teeth 32-34 will, of course, be such that when the wheels are reset the desired indicia, usually zero, will show. Also each at rest position of the wheels should show the appropriate indicia well centered with respect to the viewing position. All this follows general practice and no details appear necessary.

The important aspect of the invention is that the constantly rotating shaft through a magnetic hysteresis efiect supplies all of the torque necessary to turn all of the wheels and to work the escapements for all of the wheels excepting the one for the units wheel in this embodiment. As shown, the units escapement is electromagnetically actuated. Since the escapement for the units wheel simply releases the wheel under conditions of very low friction, the escapement mechanism can be quite light and easily moved and, therefore, the coil 62 can have verylow current requirements. The motor which drives the shaft 10 also can have very low current requirements because its torque is multiplied by reduction gearing, since it needs to run at only about 1 revolution per second and other than turning the wheels it is called upon only to work the light escapement mechanisms for the tens, hundreds and higher order wheels. Furthermore, regardless of the number of wheels, any one wheel needs to supply only enough torque to work the next escapement. It is the turning of the units wheel which releases the tens wheel and the subsequent turning of the tens wheel which releases the hundreds wheel and so on. Thus, the total torque required to be transmitted to the wheels is only that necessary for a wheel to operate one escapement when called upon to do so, times the number of wheels. The torque reaction on the shaft 10 is, as previously mentioned, at a maximum when all wheels are stationary.

If it is desired to set any number other than zero into the counter as a starting condition it is necessary in this particular embodiment merely to use a finger or a tool such as a pencil to rock the units escapement lever until the proper units number appears, then rock the tens escapement to get the proper tens digit and so on. Special control linkages or electromagnets with appropriate circuits can, of course, be provided to facilitate this or to provide for remote setting if desired.

In FIG. 2 it may be noted that the escapement pallet 48 is slightly offset relative to the plane of the pallet 46. This is not a functional requirement of a single escapement as is apparent from FIGS. 3 to 9 where it will be evident that these pallets, there shown in alignment, need not be even approximately located transversely relative to each other.'The reason for the staggered relationship shown in FIG. 2 is that as is evident in FIG. 1, the escapement levers overlap and to avoid interference they are bent as along the lines 84 so as to offset the pallets 48 rearwardly as seen in FIG. 1 relative to the pallets 46 and cam followers 66.

, In FIG. I the desire has been to show in one view the various positions of the elements rather than an actual instantaneous position. The units wheel 20 is rotated to a position where the cam 38 is illustrated in approximate elevation and the solenoid is shown in the energized condition. The tens wheel 22 is in the transition between 9 and 0 so as to show its cam 38 tripping the escapement for the hundreds wheel. The hundreds wheel is also going from 9 to 0, but is not as far advanced in this transition as is the tens wheel. Actually, of course, consistent with the positions of the tens and hundreds wheels, the cam 38 on the units wheel would not be as far advanced as showmlts true position would be just beyond the plane of the tens wheel cam follower 66 where its shape would not be evident and the solenoid would at this instant be deenergized, if the transition, as previously suggested, is at about the position of FIG. 8.

This invention as embodied in the significant portion of an electric digital type 24-hour clock is shown in FIGS. 10 to 12.

Although digital-type 12-hour clocks are common, the similar 24-hour clock presents problems which heretofore have not satisfactorily been solved on a practical basis. In a 12-hour clock there can be, figuring from the right, a seconds units wheel which readsfrom 0 to 9, a seconds tens wheel reading from 0 to 5, a minutes unit wheel reading from 0 to 9, a minutes tens wheel from 0 to 5 and an hours wheel reading from 0 to l 1. Frequently in commercial structures the seconds unit and tens wheels are omitted. In a 24-hour clock a similar approach would require an hours arrangement reading from 0 to 23, and this is not reasonable of accomplishment in a practical structure. If it is attempted to solve the problem by using a units and a tens wheel for the hours, one is confronted by the problem that the units wheel must go from 0 to 9 and then back to 0 while setting up a one on the tens wheel, then go again around to 0 at which time 2 is set up on the tens wheel and then go only to 3, so that the two wheels read 23, and then reset to 0. The problem, therefore, is how to make the hours units wheel go around twice at l0 steps each plus three more steps before resetting. The present invention provides a novel solution to this problem.

Referring to FIGS. 10, l1 and 12, the significant portion of a 24-hour clock is shown with the seconds units, seconds tens, and minutes units wheels and associated mechanism eliminated to simplify understanding and since the previously described mechanism is sufficient to disclose their structure and operation. It will be assumed that the shaft 110, similar to the shaft 10, is rotated at l revolution per second and that a cam lobe thereon, similar to the cams 38, trips an escapement mechanism similar to 'those at 42, FIG. 1, once each revolution and that this escapement mechanism releases a seconds units wheel for one increment of movement at each tripping. Alternatively, of course, a solenoid mechanism pulsed once a second, similar to that at 62-60, could be used to index the seconds units wheel at each pulse. If solenoid actuation is used, the shaft can run at any convenient reasonable speed, since timing would not depend upon shaft rotation.

The seconds units wheel indexes from 0 to 9 and indexes the seconds tens wheel one increment as it returns to 0. The

seconds tens wheel steps from to and advances the minutes units wheel one increment as it returns to 0 or blank. The minutes units wheel steps from 0 to 9 and advances the minutes tens wheel 112 as it returns to 0. Since all of the above is straightforward in view of H68. 1 to 9, FIG. 10 begins at the right with the minutes tens wheel 112. This figure also shows the hours units wheel at 114 and the hours tens wheel at 116. The instantaneous readings on these wheels is shown in H0. 1 1 as 235. The mechanism is shown approximately as it would appear just before resetting to 0. That is, at 23 hours, 59 minutes and 59 seconds, hence the reading, so far as it is illustrated, of 235.

The minutes tens wheel 112 has a hub 118 freely journaled upon the shaft 110 and this hub carries a high hysteresis disc 120 which in turn supports the rim portion 122. The hub 118 and rim portion 122 are of nonmagnetic material and the rim portion is provided with escapement teeth 124 and 126, similar to those at 32 and 34, excepting that instead of having 10 steps from 0 back to 0, they provide for 6 such steps. The rim 122 also carries the indicia 128 on its periphery and a cam 130 at the edge, similar to the cam 38 of FIG. 1, for tripping the escapement for the hours units wheel 114. In FIG. 10 this cam is intended to be illustrated in the position it would assume when the reading of wheel 112 is 5, as is shown in FIG. 11. The escapement lever 132 is like those at 42 of FIG. 1 and has pallets 134 and 136 coacting with teeth 124 and 126. It also has the equivalent at 138 of the cam following surface 66 of FIG. 1 and the bias spring 140 and limit stop 142, similar to the equivalent structure 54 and 68 of FIG. 1.

The permanent magnet ring at 144 is similar to those at 12, 14, 16 and 18-of FIG. 1 and is pressed upon a somewhat resilient hub 146 secured to the shaft 110 by a pin 148. There is a similar magnetic ring to the right of wheel 112 which is not shown but can be considered as identical. As in FIG. 1, there are grooves 150 outwardly of the teeth 124 and 126 to permit resetting wheel 112 and the others not shown, or to be discussed presently, simultaneously to 0 by moving the escapement mechanism radially outwardly according to the scheme described in connection with FIG. 1. This expedient is not essential in a clock mechanism butmay be provided as a convenience to accommodate applications where it is desired to record time intervals from some arbitrary time of beginning, such that frequent resetting to 0 is called for.

To the left of wheel 112 is a second wheel 152 which is sufficiently different in its construction and organization to require special attention. As with the previous wheel, it has a hub 154 joumaled upon the shaft 110 and this hub is provided with a high hysteresis disc 156 positioned between the magnet 144 and a similar magnet 158 which is secured to the shaft 110 similarly. The hysteresis disc 156 carries a nonmagnetic rim portion 160 which at its right edge is formed to provide radially outwardly extending teeth 162 which cooperate with pallets 164 of an escapement lever 166. The operation of this escapement is essentially similar to those previously described excepting that the two edges of the same teeth 162 can be engaged by the two pallets, since this wheel is not required to have a wide unobstructed periphery for the display of indicia as is needed by the other wheels.

As with the other escapements, completion of a revolution, resetting to 0, of the wheel 112 trips the escapement lever 166 to permit the wheel 152 to advance one increment. The pitch diameter of the toothed portion 162 of the wheel 152 is relatively'large and has 30 tooth positions thereon such that the teeth, if they were present at all positions, would require 30 impulses to step the wheel from 0 around and back to 0. The wheel, however, has certain of the teeth missing as will appear presently.

The wheel 152 is provided with a gear 168 which is meshed with an idler gear 170 free on a shaft 171. The idler is geared back by way of gears 172 on the idler and 174 on the hours units wheel 114 previously mentioned. The gearing ratio is three to one so that l revolution of the wheel 152 results in 3 revolutions of the hour units wheel 114. The hour units wheel 114 is like the wheel 112 excepting that it has the gear 174 and does not have or at least does not need the equivalent of the escapement teeth 124126. The hours units wheel 114 is equally divided around its periphery with indicia reading from 0 to 9 and back to 0.

The hours tens wheel 116 and the drive thereto may be considered identical to the wheel 112 excepting that it reads from 0 to l to 2 to 0 in one complete revolution. lts escapement mechanism is otherwise identical and similarly actuated by a cam which is not in a position to show on the edge of the hours units wheel 114. No additional description, therefore, appears to be necessary.

It was previously mentioned that some of the teeth are missing from the 30 positions on the escapement ring of wheel 152. First of all, it should be appreciated that since this wheel bears no indicia and, therefore, does not need to advance at each increment of movement the amount necessary to display a new number of appropriate size, there is no problem providing its periphery with positions for 30 equally spaced escapement teeth. These teeth at the 30 equally spaced intervals are present from 0 to 23 and are absent from the positions 24 and the others back to 0. Thus, the first 10 input pulses to the wheel 152 will rotate this wheel one third of a revolution, and because of the three to one gearing will rotate the hours units wheel 114 a full revolution from 0 through 9 and back to 0 at which juncture the hours tens wheel is released by the hours units wheel for one increment of movement from O or blank to l. The clock therefore reads 10 hours. An additional 10 input pulses to the escapement 166 rotates the wheel 152 to the two thirds position and completes an additional revolution of the hours units wheel 114, and releases the hours tens wheel for an additional increment of movement from 1 to 2. The clock then reads 20 hours.

Three additional input pulses to the escapement 166 advances the hours units wheel to 3 and brings the escapement 166 into engagement with the last tooth 162 of the continuous series on the wheel 152. The clock then reads 23 hours. Subsequently, one second after the clock reads 23 hours 59 minutes and 59 seconds, and taking the reading in reverse order, the 9 goes to 0, the 5 goes to 0 or blank, the 9 goes to 0 and the 5 goes to 0 or blank. This releases the last tooth of the wheel 152 so that it rotates from tooth 23 ahead to 0. This causes the hours units wheel to go from 3 all the way around to 0, skipping 4, 5, 6, 7, 8 and 9. The return of the hours units wheel 114 to 0 trips the escapement for the hours tens wheel so that it advances from 2 back to 0 or to a blank position. At the end of 24 hours, therefore, the clock is reset to 0.

It will be noted that although the hours units wheel 114 is driven by a gear train from the wheel 152, it nevertheless is also equipped to be advanced by the same type hysteresis mechanism as the other wheels. Although this might appear not to be necessary, it does arrange the mechanism so that the torque load on all of the hysteresis drives is approximately equal and this simplifies the design problem. Thus, the other wheels are driven by one hysteresis mechanism each while two in parallel drive the geared together wheels 152 and 114.

Although in a commercial example of the clock mechanism shown, as easily provided linkage of some sort would be included for tripping the individual escapements to set the clock to any desired starting indication, no specific mechanism has been included, since it would tend to obscure the invention. lt may be assumed, however, that beginning with the seconds units wheel, the escapement levers are rocked individually until the proper indication is set up. Usually this is most easily achieved by setting the clock slightly ahead and then starting it when the reading is appropriate. If it is desired to accommodate simultaneous resetting of all wheels to 0 as previously mentioned, the tooth 162 at the 0 position should be longer so that it will be intercepted when the escapement levers are rocked outwardly. This long tooth serves the same function as the long tooth 36 of P10. 2.

One of the advantages inherent in the invention, which is well illustrated by the 24-hour clock mechanism, is that since the escapement only is called upon to release the wheels, they being advanced by the hysteresis drive, the increments of movement with each release need not be uniform. Thus, as in the example, it is no problem to provide a wheel which advances 23 uniform steps out of 30 with 23 pulses and then jumps to position 30 on the next pulse. Similarly, the seconds and minutes tens wheels could be arranged to step off five divisions out of ten and then skip to rather than advancing from 0 around back to 0 in uniform steps. The same scheme could also, of course, be used with the hours tens wheel 116 which displays only the figures l, 2 and 0 or blank.

Having described the invention, what I claim as new and useful is:

l. A rotary stepping mechanism comprising a rotatable element, a pair of spaced apart pennanent magnets secured to said element for rotation therewith, said magnets being polarized to produce a rotating magnetic field therebetween, a high hysteresis member positioned between said magnets and within said field, said member being adapted for free rotation relative to said magnets about an axis coaxial with said element such that said member when free tends to rotate with said field, escapement means for retaining said member against rotation in any of several arcuately spaced selected positions, and means for actuating said escapement means to release said member to rotate from one retained position to another retained position under the influence of the rotating magnetic field.

2. The stepping mechanism called for in claim 1 in which said escapement means when moved in one direction from a starting position releases said member for rotation to a certain retained position and when subsequently moved in the opposite direction to the starting position releases said member for additional rotation to a certain other retained position.

3. The stepping mechanism called for in claim 2 in which the means for actuating the escapement means is an electromagnetic device.

4. The stepping mechanism called for in claim 2 in which the means for actuating the escapement means is a cam member mounted to move in a circular path coaxial with'said rotatable element and adapted to actuate said escapement means once each revolution.

5. The rotary stepping mechanism called for in claim 1 in which there are 24 evenly and closely arcuately spaced selected retained positions encompassing twenty-three-thirtieths of the circumference of said member and a space with no selected positions between the last of said selected positions and the first of said selected positions so that said stepping mechanism during each revolution makes 23 evenly spaced small steps and one large step to the point of beginning.

6. The mechanism called for in claim 5 in which there is an indicia display wheel and means for rotating said indicia display wheel 3 revolutions for each revolution of said member.

7. The combination of claim 6 in which the indicia display wheel carries evenly spaced numerals from 0 to 9.

8. The mechanism called for in claim 6 in which the indicia display wheel is coaxial with said high hysteresis member and is driven in parallel by said member and by a second high hysteresis member positioned between a pair of magnets rotated by said rotatable element, both said high hysteresis members being rotated in the same direction.

9. The rotary stepping mechanism called for in claim 1 in which the several arcuately spaced retained positions are unevenly spaced.

1 10. The rotary stepping mechanism called for in claim 1 in which some of the several arcuately spaced retained positions are evenly spaced and at least one retained position has a different spacing. 

1. A rotary stepping mechanism comprising a rotatable element, a pair of spaced apart permanent magnets secured to said element for rotation therewith, said magnets being polarized to produce a rotating magnetic field therebetween, a high hysteresis member positioned between said magnets and within said field, said member being adapted for free rotation relative to said magnets about an axis coaxial with said element such that said member when free tends to rotate with said field, escapement means for retaining said member against rotation in any of several arcuately spaced selected positions, and means for actuating said escapement means to release said member to rotate from one retained position to another retained position under the influence of the rotating magnetic field.
 2. The stepping mechanism called for in claim 1 in which said escapement means when moved in one direction from a starting position releases said member for rotation to a certain retained position and when subsequently moved in the opposite direction to the starting position releases said member for additional rotation to a certain other retained position.
 3. The stepping mechanism called for in claim 2 in which the means for actuating the escapement means is an electromagnetic device.
 4. The stepping mechanism called for in claim 2 in which the means for actuating the escapement means is a cam member mounted to move in a circular path coaxial with said rotatable element and adapted to actuate said escapement means once each revolution.
 5. The rotary stepping mechanism called for in claim 1 in which there are 24 evenly and closely arcuately spaced selected retained positions encompassing twenty-three-thirtieths of the circumference of said member and a space with no selected positions between the last of said selected positions and the first of said selected positions so that said stepping mechanism during each revolution makes 23 evenly spaced small steps and one large step to the point of beginning.
 6. The mechanism called for in claim 5 in which there is an indicia display wheel and means for rotating said indicia display wheel 3 revolutions for each revolution of said member.
 7. The combination of claim 6 in which the indicia display wheel carries evenly spaced numerals from 0 to
 9. 8. The mechanism called for in claim 6 in which the indicia display wheel is coaxial with said high hysteresis member and is driven in parallel by said member and by a second high hysteresis member positioned between a pair of magnets rotated by said rotatable element, both said high hysteresis members being rotated in the same direction.
 9. The rotary stepping mechanism called for in claim 1 in which the several arcuately spaced retained positions are unevenly spaced.
 10. The rotary stepping mechanism called for in claim 1 in which some of the several arcuately spaced retained positions are evenly spaced and at least one retained position has a diffeRent spacing. 